1. Field of the Invention
This invention relates to an apparatus which preserves modal purity in fiber optic connections where curving of the optical fiber is necessary.
2. Description of Related Art
As is well known, certain optical fibers are capable of transmitting light within mode groups. In some specialized applications, it is important to maintain the modal patterns of the light transmitted through an optical fiber over the entire length of the fiber. In these applications, system performance depends on how well the fiber optic system can contain the transmitted light within well-defined mode groups. Specifically, light injected into the fiber near the numerical aperture, i.e., high-order modes, must be well separated from light injected along the central axis of the optical fiber, i.e., low-order modes. A measure of how well the fiber optic system maintains this separation of modes is referred to as modal purity.
Specialized optical fibers and cables that maintain high levels of modal purity throughout their length are known. However, problems have been encountered in maintaining modal purity in certain regions of the fiber optic system.
More specifically in certain systems, the fiber optic cable is terminated in a strain relief mechanism, and the optical fibers continue beyond the strain relief mechanism to pin connectors. The bending of the optical fibers between the strain relief mechanism and the pin connectors produces tighter bends at the fixed points of termination, i.e., at the strain relief mechanism and the pin connectors. These tighter bends induce stresses within the optical fibers which degrade modal purity and cause micro-bending in the optical fibers which produce optical power losses in the high-order mode groups.